When a DC-DC converter is used to convert an input voltage to a desired output voltage, a settling time (transition time) is preferred to be as short as possible. The settling time is related to an inductance of an inductor within the DC-DC converter, and the smaller inductance results in a shorter setting time. However, the smaller inductance may cause a large ripple on the output voltage. Therefore, the tradeoff between the settling time and the ripple becomes a problem to a designer.
Conventional art provides a converter having additional charging path to shorten the settling time, however, the response of the circuits is generally difficult to control due to the inappropriate setting of the current provided by this additional charging path.